1. Field of the Invention
The present invention generally relates to a cylinder lock and key combination, in particular, to a cylinder lock having one or more helical keyways and an accompanying key with helical key blade(s) to fit into the keyway(s) to open the lock.
2. Description of the Related Art
The prior art presents a number of cylinder locks with one or more sets of pin tumblers and pin tumbler bores situated next to a keyway formed in a straight line parallel to the direction of key insertion. The key includes a notch edge for engaging the tumblers contained in the lock cylinder, wherein insertion of a properly mated key permits rotation of the lock cylinder within the shell to unlock or enable a controlled element in a well known manner.
U.S. Pat. No. 1,961,586 describes a key and lock construction of a core and a single set of pin-tumblers. U.S. Pat. Nos. 4,434,636 and 4,638,651 describe cylinder locks with two sets of tumblers. In the prior art, the pin tumblers are mostly situated above a straight keyway and works along the profile of the upper edge of a straight key. Alternatively, an additional set of pin tumbler may be located at the bottom or side of similar keyway and works along the profile at the bottom or side of the key.
The customary practice of breaking a lock, or opening a lock without its key, is to look through the keyway, with the aid of a special eye piece, and insert into the keyway a rod to joggle the pin tumblers so that the meeting line between the pin tumblers and its drivers (meeting line), on top of the pin tumblers, coincides with the circumference of the cylinder core to thereby turn the core. Alternatively, without viewing, the lock breaker can joggle the pin tumblers by feeling or sensing the pin tumblers with the rod and turning the core simultaneously so that the meeting line coincides with the circumference of the cylinder core allowing the lock to be opened. No matter how many sets of pin tumblers there are in the lock, an experienced lock breaker can often successfully joggle the pin tumblers to turn the core as long as he can see or feel all of the pin tumblers in the keyway Thus, the ability to see or feel and joggle with all the pin tumblers in the keyway is the essence of lock breaking or opening a lock without its key. Once one can see or feel all the pin tumblers in the keyway, one is likely to break almost any lock.
Accordingly, there is a general need in the art for a lock with enhanced security that overcomes at least the aforementioned shortcomings in the art. In particular, there is a need in the art for a key that poses tremendous difficulty for an accomplished lock-picker by not allowing the lock-picker to see all of the pin tumblers in the keyway.